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Cellular 4G/LTE Channel

Innovative RF Front End

November 14, 2012
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Innovative RF Front End

Just look at any recent smartphone or tablet, and it is a safe bet that it will be noticeably thinner than models of just a year ago. It is a trend that will continue. On the one hand, devices are getting thinner, and on the other hand, batteries, displays and functionalities are growing. The amount of space left for antennas, the device’s connection to the network, decreases by 25 percent each year.

In the past, mobile phones handled voice calls across two bands, and in some cases had Bluetooth®, GPS and Wi-Fi functionalities too. Today’s devices have to cover 2G, 3G, 4G, Bluetooth, GPS and Wi-Fi plus large amounts of data while still supporting voice calls. LTE makes that situation even more challenging:

  • There are more than 40 potential LTE bands. To enable global roaming, a device would need to support at least 13 LTE bands.
  • Some countries, including the U.S., use the low frequency 700 MHz band.
  • The number of LTE cellular antennas is double their 3G counterparts because LTE requires two antennas (MIMO) for receive diversity.

Traditional passive antennas will struggle to support LTE because they require more volume to cover the additional bands and/or the low frequency 700 MHz band. The good news is that innovations in antenna system technology can help to solve these challenges. Active antenna systems, advanced antenna structure combined with active components such as tunable capacitors and/or switches, can be used to provide advanced capabilities not possible with traditional passive antennas.

Changing the RF Landscape

Ethertronics developed EtherChip 1.0TM to address the challenges facing today’s product designers. EtherChip 1.0 uses Ethertronics’ Air InteRFace Digital Conditioning (AIRFDCTM) technology to provide a tuning function through tunable capacitance for the antenna system; seamlessly adjusting the cellular antenna’s characteristics to its dynamic requirements for optimal connectivity:

Figure 1

Figure 1 Hand and head effect correction.

Figure 2

Figure 2 Tunable antenna block diagram.

  • Reducing the antenna’s physical volume by up to 50 percent without performance tradeoffs
  • Making a wideband antenna by correcting the impedance mismatch
  • Retuning the antenna for frequency shifts
  • Offsetting hand and head effects

So even when the user’s head or hand covers the antenna, causing the antenna to detune or a frequency shift, EtherChip 1.0 adjusts the antenna to maintain the call, file download or video stream (see Figure 1).

Thin form factors will not come at the expense of voice, video and data performance with this product. All that the user notices is consistently great performance, giving the OEM’s smartphone, tablet or notebook a market differentiator. This consistency and reliability also benefits the mobile operator because those customers are far less likely to report problems. That translates into lower contact center costs, potentially making for a more positive relationship between the operator and the device OEM.

EtherChip 1.0 is designed specifically for tunability on the matching of the antenna in a shunt configuration (see Figure 2). All of the controls are linked to an SPI bus.

Figure 3

Figure 3 Capacitance value at 900 and 1800 MHz.

The capacitance versus the hexadecimal input shows a variation from 0.85 to 3.4 pF at 900 MHz and from 0.85 to 4.6 pF at 1800 MHz with 16 states (see Figure 3). Operational frequency is from 100 to 3000 MHz. Mechanical specifications include dimensions of 2.0 × 2.0 × 0.45 mm in an 8 pin QFN package. The chips are designed for surface mounting and are packaged in tape and reel. EtherChip 1.0, through a joint design with the antenna, supports all major bands and air interfaces, including 3G, LTE, LTE-Advanced and Wi-Fi, so it is a solution that OEMs can leverage across multiple product lines.

The Future Is a Versatile Antenna Front End Module

EtherChip 1.0 is the first in a series of chips that will enable the integration of the antenna front-end module (AFEM) in the space that the antenna once occupied. Leveraging the antenna’s characteristics, the AFEM architecture will be changed progressively to enable a more cost-effective, higher performance approach.

The ultimate goal for the OEMs will be to significantly reduce cost and lead-time for developing new smartphones, tablets and other mobile devices. Those savings give OEMs a competitive advantage, such as getting a hot new design to market ahead of a rival’s big launch, or reducing overhead costs so a new product can be priced profitably yet affordable enough for the mass market.

The EtherChipTM family of chips pioneers a much-needed new approach to RF front end design, one that gives device OEMs a way to turn shrinking form factors from a challenge into an opportunity. It is an idea whose time could not come soon enough.

Ethertronics Inc.,
San Diego, CA
(858) 550-3820
www.ethertronics.com

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